(a) Field of the Invention
The present invention relates to a method for mutual verifying of data ownership. More particularly, the present invention relates to a method for mutually verifying data ownership between a user terminal and a service provider server.
(b) Description of the Related Art
A technique for managing duplicated data among the data stored in a storage server managed by a storage service provider is classified into a server-side deduplication skill and a client-side deduplication skill.
In the server-side deduplication skill, while a data server has received client information, whether entire data stored during a specific time are duplicated is checked, and when duplicated data are found, one corresponding data is stored and the others are removed.
In the client-side deduplication skill, a server is allowed to check whether same data are stored when a user attempts to upload data, and when identical data are found, whether he actually has corresponding data is checked and an access right to the corresponding data is imparted to him.
Efficiency of a storage space follows a deduplication rate, so performances on respective data storage spaces of the server-side and client-side deduplication skills are equal. However, the server-side deduplication skill requires users to upload their data to the server. The client-side deduplication skill does not require him to upload his data when the same data are stored in the storage space of the server so it may substantially reduce a network load.
The client-side deduplication skill needs to accurately determine whether he actually has the data to upload since he can easily receive an access right to data when he can prove ownership of data he does not have.
A skill for verifying data ownership is used for the data deduplication skill, and differing from general encryption skills, it does not manage encrypted secret information but proves that he fully owns the corresponding data based on the owned data. That is, the skill is not based upon secret information such as an encryption key, but it generates proof that may not be generated when he does not actually own the data and proves that he owns the corresponding data based on the generated proof.
A theoretically verified skill to prove the data ownership was initially proposed by Shai Halevi, et. al, in 2011. The proposed method includes allowing a server to store a root value of a Merkle tree on original data, and, when a user attempts to prove his ownership on the corresponding data, allowing the server to select a position of a lowest node from the Merkle tree as a challenge.
The user generates hash values required by a path for calculating to the root from the node selected as a challenge, and transmits the same to the server. That is, the skill proves the ownership of the entire data with information that corresponds to a log length of the entire data by providing him with path information for generating the root value from the hash value on the random lowest node selected by him. The skills for proving the ownership under development are developed to improve the efficiency for generating ownership proving information based on the Shai Halevi scheme, or strengthen stability.
The above-noted client-side deduplication skill is based on the assumption that the data stored in the server are sufficiently well managed. That is, the user deletes his data after his ownership is proved.
Resultantly, when the data stored in the server generates a problem while he acquires the access right to the corresponding data instead of uploading the data, it is substantially impossible to restore the deleted data.
Hence, it is needed to verify whether the user as well as the server actually owns the data in the condition that a right is imparted to the data that are not uploaded.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.